8. Soft robotics¶
Research¶
This week we explore the world of soft robotics, where movement doesn't come from rigid motors or gears, but flexible materials and air and shapes. The goal of this week is to design and build soft actuators that move organically when air flows through them. One created with flexible silicone, and another one through vinyl.
Nature moves smoothly; lungs that breathe, tentacles that explore tiny creases, expanding and contracting muscles create poetry in movement. Organic movements are not programmed with code but with geometry, pressure and patience.
Soft Robotics is a branch of robotics that uses elastic or deformable materials to create structures capable of movement, adapting and handling objects. Unlike traditional robotics, it does not depend on rigid joints, but inflating internal chambers whose geometry makes them react in a smooth and organic manner. It is inspired by biology, and not machinery.
References & Inspiration¶
Inspiration for the first piece came from tentacles, specifically a mechanical tentacle controlled by 3 servos and wire (this one over here) and thought that maybe with the appropiate geometry, the same could be acomplished with soft robotics. Three concentric pieces could, in theory, create an omnidirectional tentacle. The design process was very straight-forward, it was a tentacle, with round divisions, divided in 3, with a spout for air at the top.
The design process¶
Since the piece is hollow, it was necessary to create 2 parts and then sticking them together, we have the base which has a 120° angle and the grooves for the round divisions, and the rounded geometry which is the revolved profile. We have to think of each mold in two parts also. The first mold hast the base profile extruded by 2mm for the desired thickness, and a flat piece that goes on top and makes sure that all the geometry is filled with silicone. I designed some steps on the edge of each piece so we could use butterfly clips for applying pressure.
For the second mold it was a bit more complex, since we need the curved part to be hollow, so the parts I designed are the outside part of the final piece, and the inside volume, both with a difference of around 2mm between each other. In short, when the two pieces are joined, the empty space that exists between them is the exact geometry I need in silicone.
I 3D printed the 4 parts, and added some legs and support so the piece could stay standing up while the silicone is poured. We have Smooth-on Ecoflex 30-00 silicone, which is very flexible and perfect for this kinds of applications. Very easy to use and clean, we mix part A and B on the same measure either by volume or weight, and mix thoroughly, after that we can pour the silicone, in a very thin thread so we avoid as much bubbles as we can, on both base molds, and then apply the top parts, with pressure from the clips and some rubberbands.
In theory everything worked, but in practice... Catastrophe
I came out with two solutions, adding more silicone and hope for the best, or re-doing everything. I opted for the first option and fortunately it worked very well, both pieces adhered very well. Now we had to go through this process 3 times so we have all the pieces and stick them together.
Vinyl Soft Robot The concept behind the vinyl soft robotics is two symmetrical sheets of vinyl with a defined geometry, that stick together with heat and pressure, and sandwiched between them we can find a piece of waked paper with certain geometry as well. The vinyl sticks to the other part, but not where there is wax paper, so air can flow and react, somewhat like a balloon. I personally think this technique is easier to apply to fashion design, as we can create 3D structures that breathe and can be hidden behind nice fabrics. One use-case I think would be interesting is using air as insulation for cold weathers, and this same air can change the geometry of the garment, so i will be focusing on that for the design of this piece. I have seen some patterns on jackets which can be useful for this experiment, for example the Alton Down Jacket or round geometry like the example bellow.
The areas covered with wax paper won't stick so the air will flow there, and everything will retract, creating volumes. So I designed the wax parts on Fusion 360, which then were cut on wax paper using the laser cuter, and finally ironed with a sublimation iron-press sandwiched between two pieces of textile vinyl.
And finally we have two different kinds of patterns for textile inflatable garments.
Bonus¶
This was the first soft robot I designed during my FabAcademy
Fabrication files¶
I am including the 3D files for the molds, and the 2D files for the inflatable patterns.